The present invention relates generally to turbomachines, and more particularly, to a fixture and a method for installing turbine buckets in dovetail slots of a rotor wheel by using a fixture and the dovetail slots of an adjacent spacer wheel.
Rotors for turbomachines such as turbines are often machined from large forgings. Rotor wheels cut from the forgings are typically slotted to accept the roots of turbine buckets for mounting. As the demand for greater turbine output and more efficient turbine performance continues to increase, larger and more articulated turbine buckets are being installed in turbomachines. Latter stage turbine buckets are one example in a turbine where buckets are exposed to a wide range of flows, loads and strong dynamic forces. Consequently, optimizing the performance of these latter stage turbine buckets in order to reduce aerodynamic losses and to improve the thermodynamic performance of the turbine can be a technical challenge.
Dynamic properties that affect the design of these latter stage turbine buckets include the active length of the buckets, the pitch diameter of the buckets and the high operating speed of the buckets in both supersonic and subsonic flow regions. Damping and bucket fatigue are other properties that have a role in the mechanical design of the buckets and their profiles. These mechanical and dynamic response properties of the buckets, as well as others, such as aero-thermodynamic properties or material selection, all influence the relationship between performance and profile of the turbine buckets. Consequently, the profile of the latter stage turbine buckets often includes a complex blade geometry for improving performance while minimizing losses over a wide range of operating conditions.
The application of complex blade geometries to latter stage turbine buckets presents certain challenges in assembling these buckets on a rotor wheel. For example, adjacent turbine buckets on a rotor wheel are typically connected together by cover bands or shroud bands positioned around the periphery of the wheel to confine a working fluid within a well-defined path and to increase the rigidity of the buckets. These interlocking shrouds may impede the assembly of buckets on the rotor wheel. In addition, inner platforms of these buckets may include tied-in edges, which also can impede their assembly on the rotor wheel.